/*
 * Copyright (c) 2011-2012 Alexander Dubu
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * o  Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 *
 * o  Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 *
 * o  Neither the name Axil nor the names of its contributors may be used to
 *    endorse or promote products derived from this software without specific
 *    prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

package axil.stdlib.core.construct;

import axil.api.AxilObject;
import axil.api.extend.Environment;
import axil.api.extend.Parameters;
import axil.api.extend.Source;
import axil.compiler.ast.Node;
import axil.vm.opcode.Opcode;

import java.util.List;

import static axil.framework.Functions.replace;


/**
 * A conditional value within a switch construct. For example:
 *
 * 		switch(expr,
 * 			when(value, body),
 * 			when(value, body),
 * 			else(body)
 * 		)
 */
public class When extends Conditional {
	private Opcode value;
	private AxilObject body;


	public When() {
		super();
	}


	When(Source source, Opcode value, AxilObject body) {
		super(source);
		this.value = value;
		this.body = body;
	}


	/**
	 * Relink this instruction, replacing the bad variable ID with the good
	 * variable ID. This is used when linking code that contains forward
	 * references, allowing us to compile in a single pass, but correct later.
	 */
	public void relink(int bad, int good) {
		replace(value, bad, good);
		replace(body, bad, good);
	}


	/**
	 * Emit a new instance of this function using the indicated arguments. This
	 * method can safely assume that the number of arguments required are being
	 * provided.
	 */
	public Opcode emit(Source source, List<Node> args) {
		return new When(source, args.get(0).emit(), args.get(1).emit());
	}


	/**
	 * Tell if this conditional object is selected. The condition, if any, is
	 * evaluated and a true value is returned if the condition is true.
	 */
	public boolean select(Environment env, Parameters params, AxilObject value) {
		return this.value.eval(env, params).equalTo(value);
	}


	/**
	 * Evaluate this object in the given context and environment. A non-null
	 * object must be returned.
	 */
	protected AxilObject evaluate(Environment env, Parameters params) {
		return body.eval(env, params);
	}
}
